This invention relates to a communication control device for use in controlling communication between a plurality of cordless telephone sets and a subscriber connected to the communication control device.
A conventional communication control device of the type described is used for a radio communication network which comprises a plurality of cordless telephone sets movable within a predetermined service area. Each of the cordless telephone sets is communicable with other subscribers through the communication control device by the use of radio channels composed of a plurality of radio speech channels and a control channel. In this event, the communication control device is operable to carry out outgoing call control from each of the cordless telephone sets and incoming call control to each cordless telephone set in an operation mode and to successively monitor the radio communication channels one by one in a standby mode.
Specifically, the communication control device detects in the standby mode whether each radio speech channel is idle or busy to produce idle and busy signals representative of idle and busy states, respectively. Each of the idle and the busy signals is successively memorized in a memory at every one of the radio speech channels and is successively scanned one by one at every predetermined period to detect each state of the respective radio speech channels. In other words, each state of the radio speech channels is read out of the memory at every predetermined period. The predetermined period is defined by a switching period from each radio speech channel to the radio control channel.
Recently, the radio speech channels have increased in number due to the popularity of cordless telephone sets. The switching period becomes long with an increase of the radio speech channels and thus a long time is necessary to search for an idle speech channel. Consequently, connections for an incoming call and an outgoing call can not be made within a short time between the communication control device and each cordless telephone set in the conventional communication control device.